Independent resource. Not affiliated with any utility or energy provider. Data sourced from the U.S. Energy Information Administration.Verified May 2026
Methodology: How We Calculate Electricity Costs
Every cents-per-kWh figure, every monthly-bill estimate, and every savings claim on this site traces to a single primary source. This page documents the data sources, the calculation framework, what we deliberately do not publish, and the explicit limitations of the dataset.
Primary sources
All cents-per-kWh values on the site are sourced from US government data publishers. Marketplace aggregators are not primary; they are listed in "Secondary references" below for context only.
| Source | What we take from it | Refresh |
|---|---|---|
| EIA Form 826 | State-level retail electricity rates by sector (residential, commercial, industrial). Source for every cents-per-kWh figure on the site. | Monthly (Electric Power Monthly release, first business week) |
| EIA Electric Power Monthly | National average residential rate. Anchor for the 18.05¢/kWh headline figure. | Monthly |
| EIA Form 861 | State sales, customers, and revenue. Cross-check for the per-state rate (revenue divided by sales). | Annual |
| EIA State Energy Profiles | Per-state generation mix (coal, gas, nuclear, hydro, wind, solar), consumption patterns, regulatory framework summary. | Quarterly |
| FERC | Wholesale electricity market data, interstate transmission filings, capacity market context for ISO regions. | Continuous (FERC.gov filings) |
| NARUC | State public utility commission directory, regulatory framework reference, retail-choice cluster definitions. | As updated |
| U.S. Department of Energy | Efficiency savings benchmarks (smart thermostat 10-15% HVAC, LED 75% less than incandescent, weatherization 15-25%). | As updated |
| ENERGY STAR | Certified product efficiency claims (refrigerator 15% less than standard, washing machine 25% less electricity). | Continuous (certified product database) |
State public utility commission portals
For deregulated states, the official PUC-run or PUC-approved comparison portal is the authoritative listing of supplier rates. We link to these directly from /compare-providers and /deregulated-states. Sample of the portals referenced:
| State | Portal |
|---|---|
| Texas | PowerToChoose.org |
| Pennsylvania | PAPowerSwitch.com |
| Illinois | Plug In Illinois |
| Massachusetts | MA Energy Switch |
| Connecticut | EnergizeCT |
| Maryland | MD Electric Choice |
| New Jersey | NJ Board of Public Utilities |
| New York | NYSERDA |
| Ohio | Ohio PUCO Apples-to-Apples |
| Michigan | MI Public Service Commission |
Full state-portal directory is exposed on /rates-by-state (deregulated state tools table).
Secondary references
Marketplace aggregators and consumer rate sites we are aware of. We cite their pages occasionally for cross-checking context but never as the primary source for a published figure. We do not link with affiliate parameters; their partner-supplier flow can bias which listings surface.
| Reference | How we use it |
|---|---|
| Choose Energy | Marketplace; consumer-facing rate context. Not a substitute for EIA on state averages; partner-supplier flow biases listings. |
| EnergyBot | Marketplace; commercial rate context for SMB queries. Same caveat. |
| ElectricRates | Aggregator; deregulated supplier listings. Same caveat. |
| ElectricChoice | Aggregator; cross-state regulatory framework guides. Same caveat. |
Calculation framework
Monthly bill formula
monthlyBill = (rate_cents / 100) × monthlyKwh. The cents-per-kWh rate from EIA already includes the typical residential supply + delivery + state-level taxes blended into a single retail figure. Local taxes, customer-charge fees, and rider surcharges are not captured separately.
National usage assumption
886 kWh/month per the EIA Residential Energy Consumption Survey average. State-specific usage varies (Hawaii ~500 kWh due to mild climate; Louisiana 1,107 kWh due to AC + electric heating). The calculator defaults to 886 and lets the user adjust.
Supply / delivery / tax split
The 55% supply + 35% delivery + 10% tax split used on /understand-your-bill is a cluster-wide average drawn from FERC retail rate filings and state PUC default-supply disclosures. Actual split varies by state; deregulated states usually have higher supply shares because suppliers compete; New England has a higher delivery share because of grid age.
Savings ranges
The 15-30% supply-rate savings figure assumes a typical retail-vs-default-supplier spread documented in state PUC quarterly reports. The 20-40% TOU savings assumes the household shifts 40-50% of usage to off-peak hours; lower shifts produce smaller savings. We deliberately quote conservative midpoints.
In scope
- Residential average rate per state (cents per kWh), drawn from EIA Form 826.
- Year-over-year change in state average rates.
- Regulated vs deregulated market status per state.
- Primary generation source per state (coal, gas, nuclear, hydro, wind, solar mix).
- National average monthly residential bill at the EIA-published rate and usage.
- Cents-per-kWh anchored cost-to-charge estimates for EVs at home.
- Conservative supply-shopping and TOU savings ranges anchored to state PUC reports.
Out of scope
- Live per-supplier tariff rates in deregulated markets. These move weekly and are only reliable on the supplier's own portal or the state-PUC comparison tool.
- Per-utility rate disclosures (we cite utility names but do not publish individual rate cards).
- Per-locality taxes, customer-charge fees, and rider surcharges. These vary at the city/county level and are not in EIA Form 826.
- Commercial demand charges (we discuss the concept on /business-electricity-rates but do not publish per-utility demand-charge schedules).
- Enterprise-negotiated rates and large-load tariffs.
- Wholesale market clearing prices and capacity market settlements (FERC publishes these; we do not republish).
What we deliberately do not publish
- Affiliate-tracked links to retail suppliers or marketplaces. Every external link on the site is direct.
- User-submitted live billing data. The calculator runs entirely client-side; no usage or rate input ever leaves the browser.
- ZIP-code-driven supplier matches. The state-portal links we provide are the official tool for this; we do not duplicate or compete with them.
- Original rate forecasts beyond 12 months. We surface EIA forward-looking views where they exist but do not publish independent multi-year forecasts.
Update cadence
The dataset is reviewed on the first business week of every month against the EIA Electric Power Monthly release. The single-source "Verified" stamp visible site-wide reflects the most recent verification pass.
Out-of-cycle updates are triggered when:
- EIA publishes a substantive Form 826 or Form 861 revision.
- A state PUC announces a default-supply rate change effective the following billing cycle.
- A major regulatory action (deregulation expansion, retail-choice suspension) materially changes the state framework.
- A factual error is reported via the corrections process.
Limitations
- EIA Form 826 publishes state-level averages, not utility-level. Two households in the same state with different utilities may pay materially different rates than the state average.
- The state rate dataset lags real-world rate changes by 1-3 months as EIA collects and publishes the underlying utility reports.
- Variable-rate plans in deregulated markets can move 20-50% week-to-week; site rates reflect blended state averages, not the leading-edge marginal supplier rate.
- The calculator is an estimator. Actual bills include customer charges, fees, and tax tiers that vary by locality and utility.
Corrections
Write to the address on digitalsignet.com. Factual corrections are processed within 5 business days; the dated "Verified" stamp rolls forward when a correction lands.